WO2002041690A1

WO2002041690A1 - Production line of a drip irrigation pipe and method for using said production line

Info

Publication number: WO2002041690A1
Application number: PCT/EP2001/012414
Authority: WO
Inventors: Thomas Bernauer; Eberhard Kertscher
Original assignee: Thomas Electronique Sa
Priority date: 2000-11-27
Filing date: 2001-10-22
Publication date: 2002-05-30
Also published as: EP1339274B1; EP1339274A1; EP1208741A1; ATE298499T1; DE60111767D1; AU2002216984A1

Abstract

The invention concerns a production line (1) for a drip irrigation pipe (8) comprising: a station supplying cylindrical emitters (4), an irrigation pipe (8) extruding head (6) for forming a pipe blank (28), and calibrating means (10) wherein the irrigation pipe (8) is shaped in into its final configuration, the emitters circulating in the production line (1) from the supply station (2) located upstream of said production line (1) towards the extruding head (6) located downstream of said line (1). The invention is characterised in that it further comprises a tube (36) run through by the cylindrical emitters (4) and arranged along the extruding axis of said pipe (8), said tube (36) extending on the upstream side (38) at least partly into the extruding head (6), and extending on its downstream side (4) at least partly into the calibrating means (10). The invention also concerns a method for using the production line.

Description

IRRIGATION PIPE MANUFACTURING LINE

DRIPPING AND METHOD FOR IMPLEMENTING THE SAME

OF THIS MANUFACTURING LINE

The present invention relates to the field of drip irrigation and more particularly to a method of manufacturing an irrigation pipe and a manufacturing line for implementing this method.

It is common technique to use, for certain irrigations, so-called "drip" pipes. These are pipes whose wall is pierced, at intervals of distance fixed in advance, by holes of small diameter through which the water flows into the ground. To precisely control the flow rate of the holes, there is provided, at each hole, a flow restrictor commonly called a "dripper", which may consist of a piece of hollow cylindrical plastic material which is bonded to the internal wall of the pipe. . This part has, on the side facing the inner wall of the pipe, a hollow part which forms a collecting chamber. This collecting chamber is connected to the interior space of the pipe by a conduit with calculated pressure losses, for example a conduit forming a labyrinth. This labyrinth is constituted by a groove prepared in advance on the face of the cylindrical dripper which is intended to be turned towards the internal face of the pipe.

The cylindrical drippers are manufactured individually, for example by injection of thermoplastic material. In practice, in most cases, the irrigation hose is manufactured in the following way: a polymer, polyethylene in general, is sent into an extrusion device and this continuously produces, thanks to a forming head, a tube blank in the desired dimensions. The tube blank is then brought into calibration means which fix the dimensions and the shape of the tube before cooling. As soon as the tube, still hot, leaves the extrusion head, a cylindrical dripper, brought into the extrusion head by an appropriate device, is pressed against the inner wall of the tube and sticks against it, melting locally . Once the hose-dripper assembly has cooled in a water tank, a hole is drilled in the wall of the hose, to the right of the collecting chamber.

A first drawback of such a manufacturing process lies in the way in which the drippers are brought into the extrusion head. Indeed, to bring the cylindrical drippers, there is usually provided a supply device which is in the form of a store, arranged perpendicular to the direction of extrusion of the pipe, and in which the drippers are stored. A spring pushes the drippers upwards and a device for displacement provided with a piston is provided to advance the drippers into the extrusion head and the calibration means.

One such method for fixing cylindrical drippers is, for example, described in US Patent No. 3,981,452 in the name of Eckstein. This process is distinguished in particular by a relatively slow speed of introduction of the drippers into the pipe due to the limited rate at which the drippers are pushed upwards in the supply magazine, then moved in the direction of extrusion of the pipe by the piston. Thus, so that the drippers can repeat themselves with the desired pitch in the longitudinal direction of the pipe, it is often necessary to slow down the speed of extrusion of said pipe. The assembly formed by the magazine and the piston is also mechanically unreliable and liable to jam, so that it is difficult to implement continuously. Finally, to be able to adjust the pitch with which the cylindrical drippers will repeat longitudinally in the pipe, it is necessary to adapt accordingly the frequency with which the piston pushes the drippers in the pipe. This operation is particularly delicate since the piston drive mechanism, which must be capable of transforming the rotational movement of the drive motor of said piston into a reciprocating rectilinear reciprocating movement, is particularly complex and difficult to resolve, which causes frequent failures which lead to significant quantities of waste. Typically, with a device such as that described in the Eckstein patent, it is not possible, for a given step, to introduce more than a hundred drippers and to pierce more than one hundred to one hundred and twenty meters of tube per minute, which represents a production rate. relatively low which has, of course, a negative impact on the cost price of the finished irrigation pipes. A second drawback encountered during the manufacture of irrigation pipes lies in the fact that the cylindrical drippers, for reasons related to the difficulty of precisely controlling the conditions under which they are manufactured, frequently exhibit notable imperfections of shape such as burrs resulting from molding, deformations and other irregularities which sometimes strongly distance them from the generally cylindrical shape that is sought. Thus, some drippers will present in section a profile which will be closer to that of an ellipse than a circle with a regular perimeter.

These shape defects of the cylindrical drippers have an influence on the quality of the fixing by welding of said drippers against the inner wall of the pipe, or even can cause the tearing of the pipe, which results in significant losses and therefore an increase in the cost price. this type of pipe. Indeed, the irregularly shaped drippers are introduced at the same time as the irrigation pipe in calibration means in which said irrigation pipe, still hot, will be shaped in its final configuration, while there is an attachment by hot welding of the dripper to the inner wall of the pipe. These calibration means conventionally comprise a metal sleeve having a central bore whose dimensions correspond substantially to the outside diameter of the pipe to be manufactured. Thus, a dripper which has shape defects, for example an oval section, will exert pressure on the inner wall of the pipe in formation. The inner wall of the pipe, pressing against the inner surface of the bore of the sleeve, will not be able to deform sufficiently to match the shape that the outer surface of the dripper gives it and will then tear. The present invention therefore aims to provide a line for manufacturing drip irrigation pipes devoid of the aforementioned drawbacks and in particular making it possible to avoid drippers which, in section, deviate more or less pronounced of the cylindrical shape, do not tear the material of the irrigation pipe in formation when they are fixed by heat welding on the inner wall of said pipe.

The present invention also makes it possible to introduce cylindrical drippers into the irrigation pipe without using a piston, thus avoiding any intermittent operation during the manufacturing process of this irrigation pipe. Another object of the present invention is to provide a manufacturing line of the aforementioned kind which allows easy adjustment of the pitch with which the cylindrical drippers repeat longitudinally in the irrigation pipe as well as a significant increase in the rate of manufacture of said pipe.

To this end, and according to a first embodiment, the present invention relates to a line for manufacturing a drip type irrigation pipe comprising:

- a cylindrical dripper supply station;

- an irrigation pipe extrusion head which makes it possible to form a pipe blank, and - calibration means in which the irrigation pipe is shaped in its desired configuration,

- the drippers circulating in the production line from the feed station located upstream of said production line to the extrusion head located downstream of this line, characterized in that it further comprises a tube traversed by the cylindrical drippers and arranged along the axis of extrusion of said pipe, this tube extending from the upstream side at least partly in the extrusion head, and extending from the side of its downstream end at least partly in the calibration means.

According to a complementary characteristic of the invention, the tube traversed by the drippers extends at least until the outlet of the calibration means. Thanks to these characteristics, the invention provides a system which makes it possible to prevent irregularly shaped drippers from tearing the pipe when they are fixed by heat welding to the inner wall of said pipe. Indeed, the drippers are introduced into the irrigation pipe to be fixed there only when this pipe is already, at least in part, out of the calibration means intended to give it its final shape. As the hot-setting operation of the drippers is carried out downstream of the calibration means, the expansion of the irrigation pipe is no longer, at this stage of operations, limited by said calibration means. Given its softness, the irrigation pipe will thus be able to marry without difficulty and without tearing the shape that the external surface of the dripper gives it. According to yet another characteristic of the invention, the supply station comprises metering means in which a queue is formed consisting of a succession of cylindrical drippers contiguous by their ends, said drippers progressing in the metering means at a speed lower than the speed of extrusion of the pipe, then being released by said metering means before entering the aforementioned tube.

The system according to the invention thus allows an increase in the speed of production of the irrigation pipes insofar as the drippers circulate in the production line along the axis of extrusion of said pipes and are brought continuously by the tube to beyond the calibration means. The process for bringing the drippers in accordance with the invention therefore takes place in a linear fashion, which clearly distinguishes it from the devices of the prior art in which parts animated by reciprocating movements make the drippers describe composite trajectories all of first transversely, then axially to the direction of extrusion. According to an alternative embodiment of the invention, between the metering means and the tube are provided conveying means which bring the drippers coming from the feeding station to the inlet of the tube by imparting to them a speed substantially equal to the rate of advance of the pipe in the extrusion head at the time when said drippers come into contact with said pipe.

This therefore makes it possible to bring the cylindrical drippers from the supply station at a speed lower than the speed of advance of the irrigation pipe upstream of the extrusion head, then to print to the drippers a speed substantially equal to the pipe speed after said drippers have passed through the extrusion head. By bringing each cylindrical dripper in contact with the irrigation hose at the speed of advance of the latter in the extrusion head, one avoids impacts between the drippers and the hose which could damage said hose which is still hot and deformable at this moment. Within the meaning of the present invention, the term "dripper speed"

"substantially equal" to the speed of advance of the pipe in the extrusion head, a speed of the drippers which is not more than 20% less than the speed of extrusion of the pipe, this speed being all the more close to said pipe extrusion speed that said pipe is thin. The invention is particularly advantageously applicable to thin pipes, typically less than or equal to 0.6 mm. In this way, as the relative speed between the dripper and the pipe being formed is substantially zero, any shock between them which could damage the pipe is avoided. On the other hand, for hoses of greater thickness, the speed of advance of the drippers may of course deviate further from the speed of extrusion of the irrigation hose.

According to a second embodiment, the present invention relates to a line for manufacturing a drip type irrigation pipe comprising:

- a cylindrical dripper supply station;

an irrigation pipe extrusion head which makes it possible to form a pipe blank, and

- calibration means in which the irrigation pipe is shaped in its desired configuration,

- the drippers circulating in the production line from the feed station located upstream of said production line to the extrusion head located downstream of this line, characterized in that it further comprises a metering channel traversed by the drippers, this channel being disposed on the upstream side at least partially in the extrusion head and extending inside said extrusion head as far as the outlet region of the latter. According to an additional characteristic, the position of the metering channel is axially adjustable to take into account the position of the stretching cone of the pipe being formed at the junction between the outlet of said extrusion head and the inlet of the means of calibration to determine the point where said drippers best hang on said pipe. The invention thus provides a system for manufacturing irrigation pipes which allows a further increase in rates, while still improving the quality of the installation of the cylindrical drippers, in particular as regards the constancy of their spacing and their homogeneous welding on the irrigation pipe. For example, with such a device, it is possible, for a given pitch of the drippers in the pipe, to introduce up to five hundred of these drippers into the pipe per minute. As already mentioned above in connection with the first embodiment, the position for supplying the drippers from the production line in accordance with the second embodiment of the invention comprises metering means in which said drippers progress by touching each other. their ends at a speed lower than the extrusion speed of the irrigation pipe, before being released by these metering means and entering the metering channel.

Similarly, according to an alternative embodiment, between the metering means and the metering channel are provided conveying means which inject the cylindrical drippers into the metering channel at a speed substantially equal to the speed of extrusion of the pipe. The invention also relates to a method for implementing the above manufacturing lines, characterized in that the step of introducing the cylindrical drippers consists in imparting to the drippers coming from the supply station a speed substantially equal to the speed of advance of the pipe in the extrusion head at the moment when said drippers come into contact at a point with said pipe, so that the drippers circulate in the extrusion head in the direction of extrusion of the pipe at substantially the speed of the last.

Thanks to these characteristics, the invention provides a simple and reliable system which makes it possible to obtain high flow rates during the manufacture of drip type irrigation pipes and, consequently, to reduce the cost price of such pipes. It is in particular possible to advance the cylindrical drippers at the desired speed, without having to slow down or interrupt the process of manufacturing the pipe.

Other characteristics and advantages of the present invention will appear more clearly on reading the detailed description which follows of a first and a second embodiment of a production line according to the invention, this example being given to title purely illustrative and not limiting, in conjunction with the accompanying drawings in which:

- Figure 1a is a partial schematic view in side elevation of a manufacturing line according to the first embodiment of the invention; - Figure 1b is a detail view on a larger scale of the production line shown in Figure 1a at the inlet of the calibration means; - Figure 2 is a view of an alternative embodiment of the production line shown in Figure 1a;

FIG. 3a is a view similar to that of FIG. 1a showing a production line for a drip irrigation pipe according to the second embodiment of the invention, and

- Figure 3b is a detail view on a larger scale of the manufacturing line of Figure 3a at the inlet of the calibration means.

The present invention proceeds from the general inventive idea which consists in introducing cylindrical drippers into an irrigation pipe being formed when the latter is, at least in part, taken out of the calibration means which are intended to conform it. in its final configuration. In this way, the pipe which is still hot can deform and marry, without tearing, the shape which is imparted to it by drippers which can have significant irregularities in shape. The present invention also consists in injecting the cylindrical drippers into the irrigation pipe in the direction of extrusion of this pipe, and in printing on these drippers a speed substantially equal to the speed of extrusion of said pipe, so that the process manufacturing can be done continuously and at increased speed.

According to a first embodiment of the invention, the production line shown by way of example in FIG. 1a and designated as a whole by the general reference numeral 1, successively comprises:

- a supply station 2 for cylindrical drippers 4;

- An extrusion head 6 of an irrigation pipe of the drip type 8;

means 10 for calibrating the irrigation pipe 8 downstream of which the drippers 4 are brought into contact with the inner face of said irrigation pipe 8 in order to adhere thereto, and

a cooling station 12 for the pipe 8 after extrusion and calibration.

The direction of progression of the manufacturing operations is from right to left in all of the figures appended to this patent application.

With regard to the drippers 4, it suffices, for the purposes of the present description, to note that these drippers 4 generally have the shape of a cylinder made of a plastic material and that a determined part of the surface of these drippers 4 must face the inside wall of the pipe 8.

The manufacturing process according to the invention begins with the manufacture of the cylindrical drippers 4. It continues with the introduction of these drippers 4 one after the other inside the irrigation pipe 8 while the latter is being formed. in the extrusion head 6, then calibrated in the calibration means 10. The cylindrical drippers 4 are then welded to the inner wall of said pipe 8 as and measuring the progress of this pipe 8 downstream of the extrusion head 6. Finally, the pipe 8 will be cooled in the cooling station 12 and subsequently drilled in line with each dripper 4 in order to communicate these with the outside . More specifically, upstream of the feed station 2 of the drippers 4 is arranged a vibrating bowl (not shown and known per se) with a capacity of approximately 1 m. This vibrating bowl makes it possible to sort, orient and position the cylindrical drippers 4 in the supply station 2 in accordance with the position that they must have once they are introduced into the irrigation pipe 8.

The supply station 2 comprises metering means 14 in which a queue 16 is formed consisting of a succession of cylindrical drippers 4 touching at their ends. For reasons which will be detailed later, the cylindrical drippers 4 are advanced in the queue 16 at a speed Vi lower than the speed V3 for extruding the irrigation pipe 8. This speed V-] is synchronized with the speed V3 of extrusion of the pipe 8 via a traction device (not shown and known per se) according to the relation Vi = l * n, where I is the length of a dripper 4 and n is the number of drippers introduced into the irrigation hose 8 per minute. The traction device is intended to exert a traction force on the pipe 8 at its outlet from the calibration means 10 in order to guarantee a smooth progression of said pipe 8. As can be seen in FIG. 1a, the metering means 14 consist of an accumulator channel 18 capable, for example, of containing ten to fifty drippers 4 depending on the length of the latter. The metering means 14 also comprise, in the example illustrated, a conveyor system formed by a capstan 20 consisting of two rollers 22 driven by conjugate movements and separated by a distance equal to or slightly less than the thickness of a dripper 4 .

Additionally, one of the two rollers 22 of the capstan 20 is driven by a drive motor 24 at the speed V1 lower than the speed of advance V3 of the irrigation hose 8. It goes without saying that other means of conveying can be envisaged, for example a tracked device. The extrusion head 6 can be of any known type. It has a central bore 26 which makes it possible to roughly outline a pipe blank 28 which is brought into the calibration means 10 where the irrigation pipe 8 is shaped in its desired configuration. The calibration means 10 adjoin the upstream wall 30 of the cooling station 12 which conventionally comprises a vacuum tank 32 equipped with a series of jets projecting a cooling liquid such as water. Such devices are well known to those skilled in the art. As mentioned above, the drippers 4 are driven individually at speed Vi by the rollers 22 of the capstan 20. The drippers 4 are then released by the rollers 22 and enter insertion means 34. These insertion means 34 comprise a tube 36 in which the cylindrical drippers 4 progress at the speed Vj which has been imparted to them by the rollers 22 of the capstan 20 pushing each other.

According to the invention, the tube 36 is arranged along the axis of extrusion of the pipe 8, this tube extending from the upstream side 38 at least partially in the extrusion head 6, and extending from the side of its downstream end 40 at least partly in the calibration device 10. This avoids drippers 4 with very irregular shapes from tearing the pipe 8 when they are fixed by hot welding on the inner wall of said pipe 8. Indeed , the drippers 4 are introduced into the irrigation pipe 8 to be fixed there only when this pipe 8 is already, at least in part, out of the calibration means 10 intended to give it its desired shape and which conventionally include a socket metal 42 having a central bore 44 whose dimensions correspond to those of said pipe 8. The expansion of the irrigation pipe 8 is therefore no longer, at this stage of operations, limited by the calibration means 10, so that the irrigation hose 8 will be able to absorb the irregularities of shape of the drippers 4 without tearing. According to a preferred characteristic of the invention which emerges more particularly from FIG. 1b, the tube 36 leads from the upstream end of the production line 1 downstream, passing successively through the extrusion head 6 and the blank 28 of the irrigation pipe 8, and extends at least to the outlet 46 of the calibration means 10. Advantageously, the position of the downstream end 40 of the tube 36 is axially adjustable to take into account the position of the pipe 8 at its outlet from the calibration means 10, so as to determine a point P where the cylindrical drippers 4 hang best on said pipe 8. This position adjustment, materialized by a double arrow in FIG. 1b, takes place by advancing or retreating the tube 36. It is carried out using adjustment means which will not be shown here and which are within the reach of ordinary skill in the art.

The molten plastic material is brought into the extrusion head 6 where it is shaped into a pipe. When the molten material leaves the extrusion head 6, the diameter A of the pipe 8 is larger than the final diameter B of the said pipe 8 when it leaves the calibration means 10. A suction device 48 exerts a suction force on the plastic by applying a vacuum. This vacuum is created by a vacuum pump acting on the outside diameter of the irrigation pipe 8 via channels 50 or intersecting discs. A space of height h is thus formed between the pipe 8 in formation and the tube 36 so that said pipe 8 does not adhere to said tube 36. Under the effect of the vacuum applied, the friction forces between the pipe 8 in formation and the calibration means 10 increase. This increase in friction forces must be compensated for by the traction force exerted on the irrigation pipe 8 by the traction device disposed downstream from the extrusion head 6. Since the plastic is only cooled at the surface and is therefore still soft, the tensile force causes a stretching of the irrigation pipe 8 at the same time as an increase in the extrusion speed of the latter to bring the inside diameter of the pipe 8 after calibration to the outside diameter of the dripper 4. The section, and therefore the diameter of the irrigation pipe 8, decreasing by stretching, the drippers 4 come into contact with the pipe 8 after calibration. The internal surface of the pipe 8 being still in fusion, the drippers 4 are welded to the internal wall of the pipe 8.

The distance di between the axes of the rollers 22 and the inlet of the tube 36 is less than the length I of a cylindrical dripper, so that when a dripper 4 has almost finished passing between the rollers 22, it is guided by said rollers 22 and automatically enters the tube 36.

The tube 36 has an inside diameter slightly greater than the outside diameter of the cylindrical drippers 4 to allow these drippers 4 to flow freely without risk of blockage. At the level of the extrusion head 6, the tube 36 is surrounded by a cooling jacket 52 in which circulates a thermostatically controlled fluid such as, for example, water. This cooling jacket 52 is intended to prevent the drippers 4 from melting during their passage through the extrusion head 6 and from adhering to the interior wall of the tube 36 in which they circulate. The jacket 52 comprises a duct 54 for supplying the cooling fluid. The coolant circulates in the jacket 52 and, after heating up, leaves the jacket 52 through an outlet duct

56.

The drippers 4 progress in the tube 36 by touching at their ends in the direction of extrusion of the irrigation pipe 8 at the speed Vi which is printed to them by the metering means 14. Thus, this is the ratio between the speed Vi at which the drippers 4 circulate in the tube 36 and the speed V3 of extrusion of the irrigation pipe 8 which determines the pitch with which the drippers 4 repeat along said pipe 8.

The tube 36 extends to the outlet 46 of the calibration means 10, or even beyond, so as to adjust the point P in the calibration means 10 where the diameter of the irrigation pipe 8 decreases and where the cylindrical drippers 4 cling best to pipe 8 in formation. This arrangement of the invention eliminates the problems associated with the geometry of the drippers 4.

At the outlet of the calibration means 10, the pipe 8 is cooled in the cooling station 12. Subsequently, it will be drilled in line with each dripper 4 in order to make these communicate with the outside.

According to an alternative embodiment shown in Figure 2, between the metering means 14 and the tube 36 are provided conveying means 58 which bring the drippers 4 from the supply station 2 to the inlet of the tube 36 in their printing an advance speed V2 substantially equal to or less than the advance speed V3 of the pipe 8 in the extrusion head 6 and the calibration means 10 when said drippers 4 come into contact with said pipe 8.

The cylindrical drippers 4 are therefore advanced in the extrusion head 6 and the calibration means 10 in the direction of extrusion of the irrigation pipe 8 to point P where said drippers 4 come into contact with the interior wall of said pipe 8, and printing said drippers 4 a speed V2 which is substantially equal to or less than the speed V3 of extrusion of the irrigation pipe. By speed V2 "substantially equal" to the extrusion speed V3 of the pipe 8 is meant a speed which is not more than 20% lower than the extrusion speed of the pipe 8, this speed V2 being all the more closer to said extrusion speed V3 of the pipe 8 than said pipe 8 is thin. This arrangement is particularly advantageous for thin pipes, typically less than or equal to 0.6 mm. In this way, as the relative speed between the dripper 4 and the pipe 8 in formation is substantially zero, any impact between them which could damage the pipe 8 is avoided. On the other hand, for pipes 8 of greater thickness, the advance speed V2 of the drippers 4 may of course deviate further from the extrusion speed V3 of the irrigation hose 8. To impart the advance speed V2 to the drippers 4, the conveying means 58 comprise a track 60 comprising an upper belt 62 and a lower belt 64 animated by conjugate movements and the lower 62a and upper 64a strands of which are parallel and kept apart from each other by a distance equal to or slightly less than the thickness of a dripper 4. The track 60 prints to the drippers 4 the feed speed V2 described above and brings said drippers 4 to the inlet of the tube 36.

Before starting the manufacturing operations, a queue 66 is formed in the tube 36 consisting of a succession of drippers 4 suitably oriented and touching at their ends. A dripper, ejected by the track 60, enters the tube 36 and progresses therein at speed V2 by pushing the drippers 4 which precede it. This advances the cylindrical drippers 4 to a speed V2 equal to or less than the speed V3 of extruding the irrigation pipe 8 through the extrusion head 6 into the tube 36.

When, further upstream, a new dripper 4 is brought by the conveying means 58 to the inlet of the tube 36 at speed V2, this new dripper 4 advances the drippers 4 present in the queue 66 by a distance equivalent to the length of one of these drippers 4, so that the dripper 4 which is furthest downstream in the queue 66 is ejected from the tube 36 at speed V2 and is supported by the pipe 8 in formation which gives it an acceleration and brings its speed to V ₃ . The track 60 travels at the speed V2 equal to or less than the speed of advance V3 of the irrigation pipe 8 in the extrusion head 6 and the calibration means 10. For this, the two upper 62 and lower 64 belts pass on pulleys 68 and are driven in the direction of the arrows at speed V2 by drive means such as a motor 70. Compared with the piston devices of the prior art, the track 60 has the advantage of being much simpler, and therefore more reliable from the mechanical point of view, and allow a continuous advance easy to adjust.

As will have been understood from the foregoing, the cylindrical drippers 4 which come from the vibrating bowl arrive one after the other by forming a line 16 in which they touch each other at their ends at the height of the metering means 14. There, the drippers 4 are driven individually at speed V1 by the rollers 22 of the capstan 20. The drippers 4 are then released by the rollers 22 and transferred to the track 60. Preferably, the distance d2 between the axes of the rollers 22 and the axes pulleys 68 over which the belts 62 and 64 of the track 60 pass is less than the length I of a dripper 4, so that, when a dripper has almost finished passing between the rollers 22, it is automatically taken in load by track 60.

Of course, other devices for transferring the drippers 4 from the metering means 14 to the conveying means 58 can be envisaged.

On the track 60, the cylindrical drippers 4 are brought to a speed V2 which can be chosen equal to or less than the speed V3 at which the irrigation pipe

8 progresses through the calibration means 10 and the downstream part of the manufacturing line 1. When the speed V2 at which the track 60 travels little differs from the speed V3 in advance of the irrigation pipe 8 in the head extrusion 6, it is the speed V1 at which the drippers 4 pass through the metering means 14 which determines the distance or not with which said drippers 4 will repeat in the longitudinal direction of the irrigation pipe 8. Thus, the higher the speed V1 will be lower than the speed V2, the more the pitch between two successive cylindrical drippers 4 in the pipe 8 will be tall. Conversely, the closer the speeds Vi and V2 are to one another, the closer the drippers 4 are to each other.

Thanks to the present invention, it is therefore possible to adjust very precisely and without having to interrupt the manufacturing process the pitch with which the cylindrical drippers 4 are repeated in the irrigation pipe 8, simply by adjusting the linear speed V1 at which the drippers 4 pass between the two rollers 22 of the capstan 20.

In addition, the means used, namely the capstan 20 and the track 60, are extremely simple and therefore reliable and not very prone to breakdowns.

In all that follows, the elements identical to those described previously in connection with FIGS. 1a and 1b will be designated by the same reference numerals. For a detailed description of these various elements, reference will be made to the relevant passages of the preceding description of the embodiment shown in FIGS. 1a and 1b.

The production line shown in Figure 3a is in accordance with a second aspect of the invention. Designated as a whole by the general reference numeral 72, this production line comprises, analogously to the production line described in connection with FIG. 1a:

- a supply station 2 for cylindrical drippers 4;

an extrusion head 6 of an irrigation pipe 8 in which the cylindrical drippers 4 are brought into contact with the inner face of said irrigation pipe 8 to adhere to it, and

a cooling station 12 for the pipe 8 after extrusion and calibration of the latter.

A vibrating bowl (not shown and known per se) allows the cylindrical drippers 4 to be placed in the supply station 2 in accordance with the position that these drippers 4 must have once they are introduced into the irrigation pipe 8 This vibrating bowl is arranged upstream of the supply station 2 of the drippers 4.

The supply station 2 comprises metering means 14 in which a queue 16 is formed consisting of cylindrical drippers 4 touching at their ends. The drippers 4 progress in the queue 16 at a speed V1 lower than the speed V3 for extruding the irrigation pipe 8.

As previously, the metering means 14 consist, in the example illustrated, of a capstan 20 formed of two rollers 22 and will therefore not be described in more detail here. The cylindrical drippers 4 which come from the vibrating bowl arrive one after the other by touching by their ends at the height of the metering means 14. There, the drippers 4 are driven individually at speed V1 by the rollers 22 of the capstan 20. The drippers 4 are then released by the rollers 22 and enter a guide system which can, for example, take the form of a metering channel 74. According to the invention, this metering channel 74 , crossed by the drippers 4, is disposed on the upstream side at least partially in the extrusion head 6 and extends inside said extrusion head 6 as far as the outlet region 76 of the latter. More specifically, the metering channel 74 extends between the metering means 14 and the point P where the cylindrical drippers 4 are supported by the irrigation pipe 8 being formed at the outlet 76 of the extrusion head 6. The metering channel 74 encounters on its path a cooling device 78 intended to prevent the drippers 4 from melting during their passage through the extrusion head 6. In this cooling device 78 circulates a thermostatically controlled cooling fluid such as that, for example, water, which arrives via a supply duct 80 and which leaves the cooling device 78 after being heated by an outlet duct 82. So that the cylindrical drippers 4 come into contact with the irrigation pipe 8 after extrusion, the section of the pipe 8 is reduced by stretching and, consequently, the diameter of said pipe 8 decreases proportionally. The diameter of the pipe 8 decreasing, the drippers 4 come into contact with the inner wall of the pipe 8 which is still hot. As a result, the surface of the drippers 4 melts and binds with the pipe 8.

This last point clearly emerges from FIG. 3b which is a detail view on a larger scale of the production line 72 according to the second aspect of the invention at the junction between the extrusion head 6 and the calibration means 10. As explained above, the drippers 4 pass through the extrusion head 6 where the molten plastic is formed to produce the irrigation pipe 8. In general, the diameter C of the molten material at the outlet 76 of the extrusion head 6 is larger than the diameter D of the calibration means 10. These calibration means 10 are necessary to give the finished product the desired dimension. They include, as in the previous example, a metal sleeve 42 having a central bore 44 whose dimensions correspond to the final shape that we want to print on the irrigation pipe 8. In the present case, the extrusion tools are shaped in such a way that the internal diameter E of the irrigation pipe 8, once supported by the calibration means 10, is equal to or smaller than the external diameter F of a cylindrical dripper 4. The drippers 4 are therefore brought into the pipe 8 during calibration and are driven by the latter. The welding of the drippers 4 with the pipe 8 takes place from this moment there. Once a dripper 4 has been taken loaded by the pipe 8, the location that this dripper 4 occupied at the outlet of the extrusion head 6 is found free.

It will be noted that, according to another characteristic of the invention, the position of the metering channel 74 in which the drippers 4 circulate inside the extrusion head 6 is axially adjustable to take into account the position of the cone of stretching 84 of the molten material at the junction between the outlet 76 of the extrusion head 6 and the inlet of the calibration means 10. More precisely, the outlet of the metering channel 74 is approached as close as possible to said stretch cone 84 in order to determine the position in which the drippers 4 best hang on the pipe 8 in formation. This position adjustment, materialized by a double arrow in FIG. 3b, takes place by approaching or moving the outlet of the metering channel 74 away from the inlet of the calibration means 10. It is carried out using means of adjustment not shown and known to those skilled in the art.

At the outlet of the calibration means 10, the pipe 8 will be cooled in the cooling station 12 and subsequently drilled at the right of each dripper 4 in order to make the latter communicate with the outside.

As in the example illustrated in FIG. 1a, the extrusion head 6 has a central bore 86 which makes it possible to roughly blank the pipe blank 28 which will then be brought into the calibration means 10 where the pipe 8 will be conformed to its desired configuration. The calibration means 10 adjoin the upstream wall 30 of the cooling station 12 which will not be described in more detail here.

It goes without saying that the invention is not limited to the embodiments which have just been described, and that modifications and variants can be envisaged by a person skilled in the art without departing from the scope of the present invention. In particular, similar to the variant embodiment of the invention shown in connection with FIG. 2, conveying means 58 such as, for example, a track 60 with belts 62 and 64 can be provided between the metering means 14 and the metering channel 74. These conveying means 58 will bring the drippers 4 coming from the feeding station 2 to the inlet of the metering channel 74 by imparting to them a speed V2 substantially equal to or less than the speed of advance V3 of the pipe 8 in the extrusion head 6 when said drippers 4 come into contact with said pipe 8. Before starting the manufacturing operations, care will have been taken to form a queue in the dosing channel 74 66 consisting of a plurality of drippers 4 in contact at their ends. Thus, when a dripper 4 is ejected by the track 60, it will enter the metering channel 74 and progress therein at speed V2 by pushing the drippers 4 present in the queue 66 by an equivalent distance to the length of one of these drippers 4, so that the dripper 4 which is furthest downstream in the queue 66 will be ejected from the metering channel 74 at speed V2 and will be taken up by pipe 8 in formation which will give it acceleration and bring its speed to V3.

It goes without saying that the invention is not limited to the embodiments which have just been described, and that modifications and variants can be envisaged without departing from the scope of the present invention.

Claims

1. Manufacturing line (1) of an irrigation pipe (8) of the drip type comprising:

- a supply station (2) of cylindrical drippers (4);

an extrusion head (6) of the irrigation pipe (8) which makes it possible to form a pipe blank (28), and

- calibration means (10) in which the irrigation pipe (8) is shaped in its desired configuration,

- the drippers (4) circulating in the production line (1) from the feed station (2) located upstream of said production line (1) towards the extrusion head (6) located downstream of this line (1), characterized in that it further comprises a tube (36) traversed by the cylindrical drippers (4) and arranged along the axis of extrusion of said pipe (8), this tube (36) extending from upstream side (38) at least partly in the extrusion head (6), and extending on the side of its downstream end (40) at least partly in the calibration means (10).

2. Manufacturing line according to claim 1, characterized in that the tube (36) extends at least as far as the outlet (46) of the calibration means (10).

3. Manufacturing line according to claim 2, characterized in that the position of the downstream end (40) of the tube (36) is axially adjustable to take into account the position of the pipe (8) at its outlet from the calibration means (10), so as to determine the point where the cylindrical drippers (4) best hang on said pipe (8).

4. Manufacturing line according to any one of claims 1 to 3, characterized in that the calibration means (10) comprise suction channels (50) cooperating with a suction device (48) to exert a force suction on the irrigation hose (8) being formed by applying a vacuum, so that a space is formed between said hose (8) and the tube (36) and that a friction force between the pipe (8) and the calibration means (10) is generated.

5. Manufacturing line (72) of an irrigation pipe (8) of the drip type comprising:

- a supply station (2) of cylindrical drippers (4);

- calibration means (10) in which the irrigation pipe (8) is shaped in its desired configuration, - the drippers (4) circulating in the production line (72) from the feed station (2) located upstream of said production line (72) towards the extrusion head (6) located downstream of this line (72), characterized in that it further comprises a metering channel (74) crossed by the drippers (4), this channel (74) being disposed on the upstream side at least partially in the extrusion head (6 ) and extending inside said extrusion head (6) as far as the outlet region (76) of the latter.

6. Manufacturing line according to claim 5, characterized in that the position of the metering channel (74) is axially adjustable to take into account the position of the stretching cone (84) of the pipe (8) being formed at the junction between the outlet (76) of said extrusion head (6) and the inlet of the calibration means (10) in order to determine the point where said drippers (4) best hang on said pipe (8).

7. Manufacturing line according to any one of claims 1 to 6, characterized in that the supply station (2) comprises metering means (14) in which is formed a queue (16) consisting of a succession of cylindrical drippers (4) contiguous by their ends, said drippers (4) progressing in the metering means (14) at a speed (Vi) lower than the extrusion speed (V3) of the pipe (8).

8. Manufacturing line according to claim 7, characterized in that the metering means (14) comprise an accumulator channel (18) in which the drippers (4) travel by touching at their ends before being supported by a capstan (20) formed by two rollers (22) driven by conjugate movements and separated by a distance equal to or slightly less than the thickness of a dripper (4).

9. Manufacturing line according to any one of claims 7 or 8, characterized in that upstream of the extrusion head (6) are provided conveying means (58) which bring the drippers (4) from the feed station (2) up to the inlet of the tube (36), respectively of the metering channel (74), by imparting to them a speed (V2) substantially equal to the speed of advance (V3) of the pipe ( 8) in the extrusion head (6) when said drippers (4) come into contact with said pipe (8).

10. Manufacturing line according to claim 9, characterized in that the conveying means (58) comprise a track (60) comprising an upper belt (62) and a lower belt (64) which are driven by conjugate movements and whose respective lower (62a) and upper (64a) strands are parallel and kept apart from each other by a distance equal to or slightly less than the thickness of a cylindrical dripper (4), the track (60) bringing the drippers (4) to the inlet of the tube (36), respectively of the metering channel (74).

11. Manufacturing line according to any one of claims 1 to 10, characterized in that, at the level of the extrusion head (6), the tube (36), respectively the metering channel (74), pass through a cooling jacket (52, 78) intended to prevent the drippers (4) from melting during their passage through the extrusion head (6) and in which circulates a thermostatically controlled cooling fluid which arrives via a supply pipe ( 54, 80) and which leaves said cooling device (52, 78) after being heated by an outlet duct (56, 82).

12. Manufacturing line according to any one of claims 1 to 11, characterized in that the calibration means (10) are arranged at the inlet of a cooling device (12) which comprises a vacuum tank (32 ) equipped with a plurality of jets projecting a cooling liquid to cool the irrigation pipe (8) at its outlet from said calibration means (10).

13. Method for implementing the manufacturing line according to any one of claims 1 or 5 in that they depend on claim 9, characterized in that the step of introducing the cylindrical drippers (4) consists to print to the drippers (4) coming from the supply station (2) a speed (V2) substantially equal to the speed of advance (V3) of the pipe (8) in the extrusion head (6) at the time when said drippers (4) come into contact at a point (P) with said pipe (8), so that the drippers (4) circulate in the extrusion head (6) in the direction of extrusion of the pipe (8) substantially at the speed of the latter.

14. Method according to claim 13, characterized in that the speed (V2) is not more than 20% lower than the speed of advance (V3) of the irrigation pipe (8).